This invention relates generally to apparatus, systems and methods for collecting and mixing two biological/pharmaceutical liquids and, in particular, for collecting whole blood from a donor to minimize lesion of collection caused by unproportional mixing with anticoagulant fluids.
During conventional collection procedure, fresh, whole blood taken from a donor is passed to a collection bag already containing an amount of anticoagulant-storage or anticoagulant liquid needed to prevent the entire amount of blood to be collected from coagulating within the collection bag. These anticoagulants, such as ACD, CPD and CPD-Adenine, are strongly acidic, having a pH range of 4.95 to 5.63, and high in a complexing agent, citrate, that strips red cells of essential cations, Ca.sup.+2 and Mg.sup.+2. Customarily, a full unit or 450 ml of blood are mixed with 63-75 ml of anticoagulant.
The anticoagulant is present in full amount in the blood collection bag at the beginning of the process and whole blood is then mixed with this solution as it is collected. When the first approximately 100 ml of donor blood is drawn into the required volume of anticoagulant used for a full unit of stored blood, the red cells are initially subjected to an environment greatly altered from the one encountered in vivo and are irreparably damaged thereby. This damage to the red blood cells is referred to herein as the lesion of collection, although there are other factors causing lesion of collection.
This lesion of collection problem is discussed in "The Influence of Extra-Cellular Factors Involved in the Collection of Blood in ACD on Maintenance of Red Cell Viability During Refrigerated Storage" by John G. Gibson, et al., at p. 855 et seq. of the August 1956 issue of The American Journal of Clinical Pathology. Reference may be made to that paper for a thorough discussion of the problems. Briefly, Gibson found that this 100 ml of blood collected into the full volume of the anticoagulant solution underwent deleterious changes in their in vitro parameters, and that such changes correlated well with loss in post-transfusion survival of similarly treated red cells. Further, comparison of literature values indicated that post-transfusion survivals for full units of anticoagulant mixed whole blood were approximately the same after 21 days of storage as the volume percentage of whole blood found to be most injured during the initial stage of collection. These observations are reported to indicate that a significant contribution to loss in red cell post-transfusion viability and function results from the trauma induced during initial stages of collection of blood from the donor.
The anticoagulants have been carefully designed to minimize this lesion. However, for a number of technical reasons, no known anticoagulant fluid has been devised that completely eliminates this lesion of collection. Most work to date has been aimed at reducing the factors causing lesion during storage.